This week's report that U.S. government surveillance efforts have reached our roads appears to be just the latest troubling expansion of post-Sept. 11 domestic spying. Like so many of the online surveillance techniques that have been revealed in recent years, the newly uncovered Justice Department program -- which scans license plates in order to track the movements of vehicles, creating a national database for law enforcement agencies -- gathers huge amounts of data about the movements of innocent and guilty people alike. But, like the rise of government cybersurveillance, the rise of auto surveillance has happened so rapidly and completely that the public may only be waking up to it long after it has become an ineradicable fixture of modern American life.

According to the report, in addition to installing cameras on public roads, the Justice Department's Drug Enforcement Administration taps into a massive and growing network of license plate scanners operated by various local law enforcement agencies. These plate reading programs, helped by grants from the Department of Homeland Security, are now operated by as many as 70 percent of local police departments, which see them as a "force multiplier" for overworked beat cops. With the ability to automatically scan more than 100,000 vehicles per day at an ever-lower cost, police say the devices simply make officers more efficient at their jobs.

That same efficiency argument is also responsible for proliferating license plate scanners in the private sector, where they are largely used for debt collection. As the Boston Globe reported, a nationwide network of unmarked cars armed with automated plate readers hoovers up data from cars in order to find cars that are stolen or in default, making a once-painstaking process as easy as making the morning commute. These private firms assert that collecting the data is covered by the First Amendment, even when they make their data pools available to law enforcement agencies. And given the growing importance of auto credit expansion to car sales, it seems that these private plate scanners have come to play a critical role in the new economy -- and they are unlikely to simply disappear due to privacy concerns.

Moreover, the endgame for automotive privacy is already within sight. With the most recent push for a gas tax increase now apparently off the table, only one real alternative remains: a so-called vehicle miles traveled tax. This tax, which was floated by former Transportation Secretary Ray LaHood, would track cars centrally and tax them based on the number of miles they are driven. Such a system is being tested here in Oregon as a way of ensuring that electric vehicles pay for their road use. And if politicians continue to resist raising gas taxes at the federal level, it's only a matter of time before every car in America is tracked by the federal government in order to collect funds for highway construction and maintenance.

It appears a new reality is emerging in which simply leaving home in your car makes you a likely target of surveillance. But, as efficient and effective as license plate scanners appear to be, they carry huge costs as well. The auto industry -- which is already struggling to maintain its long-term marketing strategy of associating car ownership with that emotional touchstone personal freedom -- may find that these profound social shifts further erode its pitch that "we don't sell cars, we sell freedom." And without their appeal to freedom, automobiles will struggle to compete with more pragmatic (if nontraditional) alternatives such as car sharing and even public transportation.

But the use of license plate scanners and other car surveillance techniques may already be so embedded as to prevent any rollback. And with private companies leading the way in normalizing surveillance in the name of financial savings -- as Progressive Insurance has done with its Snapshot program, which offers discounts in return for collecting data about driver activity and behavior -- the public may already be so inured to it as to quell any public outrage to the recent revelations. This is dangerous not only because the rise of automotive surveillance raises questions about privacy and presents opportunities for abuse, but also because it crept up on the public without an open debate about how to weigh its benefits against its costs.

The only question now is whether the debate is happening too late. Having emerged in relative secrecy, automotive surveillance may now be so deeply ingrained in U.S. law enforcement and the economy as to be out of the public's control, and too valuable to be dispensed with over such trivialities as personal privacy. If so, we might assume that the expectation of privacy ends as soon as we leave our homes.

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